Pathogenetic links in metabolic syndrome and urolithiasis

Metabolic syndrome is defined as a plethora of separate abnormal labora­tory parameters and clinical features that increases the risk of cardiovascu­lar diseases and type II diabetes mellitus.

Epidemiologic data indicates sig­nificant associations between uro­lithiasis and metabolic syndrome or separate components of this hetero­genous entity. This review focuses on the general pathogenesis of metabolic syndrome and on the pathogenesis of urinary tract calculi (of calcium and uric acid type) formation if a back­ground of obesity/insulin resistance is evident. We also reviewed several re­cent studies that investigated possible pathogenetic links between insulin re­sistance and urolithiasis.

Although calcium oxalate stones are the type most often encountered in the general popul ation, there is an in­creased frequency of uric acid stone for­mation in patients with metabolic syn­drome or diabetes mellitus. It is consid­ered that impaired ammoniogenesis decreases urinary pH values, resulting in precipitation of uric acid and forma­tion of urinary stones. Plenty of epide­miological data suggest that insulin re­sistance is very significant in the for­mation of kidney stones. This informa­tion is confirmed by articles indicating a direct correlation between insulin concentrations in blood and urine pH and supporting the existence of insulin receptors in the wide system of nephrons.

Not many articles discuss the for­mation of calcium stones if several com­ponents of metabolic syndrome are evi­dent. Data on this subject is quite frag­mented, and although this article men­tions several potential mechanisms concerning how insulin resistance may lead to the formation of calcium stones, there is still a lack of information sug­gesting that these mechanisms are significant.

Keywords: metabolic syndrome, renal calculi, obesity, insulin resistance, dia­betes mellitus.